CQPPS: A scalable multi‐path switch fabric without back pressure

Abstract

Generally, in order to guarantee a good throughput and decrease the complexity of reassembling, the majority of current commodity routers take elaborate closed-loop flow control schemes such as back pressure to prevent cell loss in the switch fabrics. As commodity router's port number grows larger and link rate becomes faster, the huge I/O pins and memory consumption makes these closed-loop flow controls very difficult to implement engineeringly. This paper approaches the problem of building ultra-large-capacity router from a different angle. Crosspoint-queued-based Parallel Packet Switch (CQPPS), a highly scalable switch architecture with no need of any closed-loop flow control schemes, is proposed. And the authors propose the Padded Frame plus Round-Robin scheduling scheme for CQPPS architecture. By allowing potential cell loss in the switch fabrics and slightly higher light-load delay, CQPPS achieves loss rate orders of magnitudes lower than back pressure schemes, and high-load delay 10 times less than back pressure schemes. It also greatly reduces the complexity of engineering implementation.